Suspensions for commercial vehicles, are often complex and expensive. It is challenging to efficiently package multiple suspension components, such as spring elements and shock absorbers, within a designated packaging space. The spring elements and shock absorbers must be free of other vehicle underbody components that spin and/or articulate during vehicle operation. For example, the spring elements and shock absorbers cannot interfere with the operation of a drive shaft in a drive axle configuration. The spring elements and shock absorbers also cannot interfere with movement of a knuckle assembly in a steering axle configuration, and cannot interfere with movement of an upper control arm in independent suspension applications.
Additional challenges are presented by vehicle applications that have extreme ranges of wheel travel. Further, many systems require suspensions that are ride height adjustable and load level adjustable over a significant range of axle loading. This further complicates systems and increases costs.
Traditional torsion bar independent suspensions use either an upper or lower control arm to twist a length of a tube or rod to act as a torsion spring. Ride height and static load are manually adjusted by a jack-screw mechanism located at a grounded end of the torsion springs at a vehicle chassis. Effective lengths of the torsion springs are fixed. Jounce stiffness is determined by the arm and the rate of the full length of the torsion spring. Roll stiffness is determined by the vertical rate at opposite wheels. If additional roll stiffness is required, an auxiliary sway bar may be incorporated into the suspension system.
Thus, there is a need for a simple and effective suspension system capable of providing desired roll and jounce stiffness as well as being ride height adjustable and load level adjustable.